1. Field of the Invention
The present invention relates to devices and methods to deliver thin film materials onto substrates using near atmospheric pressure (or alternatively above atmospheric pressure) generated ions, ion clusters, or charged particles (droplets and/or solid particles) as the material form, or as a precursor to reaction products that are the material form. The technique relies on the use of ion and particle generators in combination with shaped, patterned, conformal ion lenses and individually addressable elements of a lens array to create an integrated deposition system for printed patterns of thin films. The devices and methods provide a novel approach to delivering materials to a surface, removing materials from a surface, or creating new materials at or on the surface. Transport of material to and away from the surface is precisely controlled spatially, temporally, and compositionally. These methods and devices may be used in applications of thin film deposition, micro-electronics and semi-conductor manufacturing, printing, surface interfacial layers, coating, painting, sample and reagent treatment, preparation for sensors, chemical analysis, and 3-dimensional structures and devices as diagramed in FIG. 1.
2. Description of Related Art
The application of inks is well known in the graphic arts, publishing and printing inks industries. A new and emerging area in printing is the ability to print organic electronic devices using complex materials in thin films, rapidly and at atmosphere (1).
Printing materials for graphics arts products typically is through five major routes: offset lithography, letterpress, gravure, screen print and xerography. Printing materials for electronic purposes demands more stringent requirements for contiguous thin film multilayer applications, and has been primarily demonstrated with inkjet technology, photolithographic patterning, stenciling, microcontact printing, or print and etch methods that use artwork and photoprocesses.
The application of organic, inorganic, biomolecular thin films using vacuum based processes is a common practice, however, atmospheric processes for thin film deposition have been of limited practice (2). This citation focuses on the use of electrosprayed ions of biomolecules to create multiple deposits of any size and form through a dielectric mask that covered a slightly conductive substrate.
A comprehensive summary of the classical approaches to ion generation and processing is reviewed in reference (3). Ions are typically generated with one or more plasma or discharge devices that operate at reduced pressure. Ion beam technologies are summarized in reference (4).
In microelectronics, circuit fabrication involves a number of steps carried out primarily under vacuum and sequentially as follows,                1. Epitaxial growth of doped Si or GaAs layers on Si or GaAs substrate        2. Ion implantation of dopants (B an P into Si, Si into GaAs) selective in depth and location. The implant damage must be annealed out.        3. Ion Implantation of non-dopants (e.g. protons) to deliberately cause damage thus lowering the conductivity to provide electrical isolation of devices.        4. Deposition of dielectric layers to isolate the conductive layers.        5. Patterning a mask to define specific features. This usually involves covering the wafer with photosensitive material (resist), exposing it to energy (ultraviolet or x-ray photons, electrons, or ion beams) to change its structure locally so that a pattern can be developed.        6. Etching the pattern in the semiconductor (e.g. GaAs) in one of the dielectric layers (e.g. Si3N4) or in metal film (e.g. Al).        7. Planarization of the surface to allow for the next process step.        8. Deposition of polycrystalline semiconductor, particularly Si, for transistor gates.        9. Cleaning between process steps. There may be 10-12 mask levels each requiring a different process step and a clean surface. Since each mask involves photolithography, removal of residual resist at each stage is vital.        
The requirement of each of these steps to be performed under vacuum creates substantial cost and complexity. The present device addresses alternative atmospheric pressure processes that may replace some of the low-pressure processes with cheaper and possibly more precise surface processes.
The generation of ions and charged particles at atmospheric pressure is accomplished by a variety of means; including, electrospray (ES), atmospheric pressure chemical ionization (APCI), atmospheric pressure matrix assisted laser desorption ionization (AP-MALDI), discharge ionization, 63Ni sources, inductively coupled plasma ionization (ICP), and photoionization. A general characteristic of all atmospheric sources is the dispersive nature of the ions once produced. For example, needle sources such as ES and APCI disperse ions radially from the axis in high electric fields emanating from needle tips. Aerosol techniques disperse ions in the radial flow of gases emanating from tubes and nebulizers. Even desorption techniques such as AP-MALDI will disperse ions in a solid angle from a surface. The radial cross-section of many dispersive sources can be as large as 5 or 10 centimeters in diameter. As a consequence of a wide variety of dispersive processes, efficient sampling of ions from atmospheric pressure sources to small cross-sectional targets or through small cross-sectional apertures and tubes (usually less than 1 mm) into a targeted small region in space becomes quite problematic. This is particularly amplified if the source of ions is removed from the regions directly adjacent to the target surface or transmission aperture. Clearly, there is a need for improvement by optical means of transmitting and controlling ions and charged particles from dispersive sources to deposition surfaces.
Approaches for sampling ions at atmospheric pressure is exampled by the approaches used to interface atmospheric ion sources to mass spectrometers. The simplest approach to sampling dispersive atmospheric sources into vacuum is to position the source on axis with a sampling aperture or tube. The sampling efficiency of simple plate apertures is generally less than 1 ion in 104. A device disclosed in U.S. Pat. No. 4,209,696 to Fite (1980) used pinhole apertures in plates with electrospray. Devices disclosed in U.S. Pat. No. 5,965,884 (1999) and W.O. patent 99/63576 (1999) to Laiko and Burlingame used aperture plates with atmospheric pressure MALDI. Atmospheric pressure sources disclosed in Japanese patents 06060847 A to Kazuaki et al (1992) and 11230957 A to Hiroaki (1998) are also representative of this inefficient approach. This general approach in severely restricted by the need for precise aperture alignment and source positioning and very poor sampling efficiency.
Wide varieties of source configurations utilize conical skimmer apertures in order to improve collection efficiency over planar devices. This approach to focusing ions from atmospheric sources is limited by the acceptance angle of the field generated by the cone. Generally, source position relative to the cone is also critical to performance, although somewhat better than planar apertures. Conical apertures are the primary inlet geometry for commercial ICP mass spectrometers with closely coupled and axially aligned torches. Examples of conical-shaped apertures are prevalent in ES and APCI inlets, for example U.S. Pat. No. 5,756,994 to Bajic (1998); and ICP inlets, U.S. Pat. No. 4,999,492 to Nakagawa (1991). As with planar apertures, source positioning relative to the aperture is critical to performance and collection efficiency is quite low.
One focusing alternative utilizes a plate lens with a large hole in front of an aperture plate or tube for transferring sample into the vacuum system. The aperture plate is generally held at a high potential difference relative to the plate lens. The configuration creates a potential well that penetrates into the source region and has a significant improvement in collection efficiency relative to the plate or cone apertures. This configuration has a clear disadvantage in that the potential well resulting from the field penetration is dependent of ion source position, or potential. High voltage needles can diminish this well. Off-axis sources can affect the shape and collection efficiency of the well. Optimal positions are highly dependent upon both flow (gas and liquid) and voltages. They are reasonable well suited for small volume sources such as nanospray. Larger flow sources become less efficient and problematic. Because this geometry is generally preferential over plates and cones, it is seen in most types of atmospheric source designs. We will call this approach the “Plate-well” design that is reported with apertures in U.S. Pat. No. 4,531,056 to Labowsky et al. (1985), U.S. Pat. No. 5,412,208 to Covey et al. (1995), and U.S. Pat. No. 5,747,799 to Franzen (1998). There are also many Plate-well designs with tubes reported in U.S. Pat. No. 4,542,293 to Fenn et al. (1985), U.S. Pat. No. 5,559,326 to Goodley et al. (1996), and U.S. Pat. No. 6,060,705 to Whitehouse et al. (2000).
Several embodiments of atmospheric pressure sources have incorporated grids in order to control the sampling. U.S. Pat. No. 5,436,446 to Jarrell and Tomany (1995) utilized a grid that reflected lower mass ions into a collection cone and passed large particles through the grid. This modulated system was intended to allow grounded needles and float the grid at high alternating potentials. This device had limitations with duty cycle of ion collection in a modulating field (non-continuous sample introduction) and spatial and positioning restrictions relative to the sampling aperture. U.S. Pat. No. 6,207,954 B1 to Andrien Jr. et al (2001) used grids as counter electrodes for multiple corona discharge sources configured in geometries and at potentials to generated ions of opposite charge and monitor their interactions and reactions. This specialized reaction source was not configured with high field ratios across the grids and was not intended for high transmission and collection, rather for generation of very specific reactant ions. An alternative atmospheric pressure device disclosed in Japanese patent 11288683 A to Yoshiaki (1998) utilized hemispherical grids in the second stage of pressure reduction. Although the approach is similar to the present device in concept, it is severely limited by gas discharge that may occur at low pressures if higher voltages are applied to the electrodes and most of the ions are lost at the cone-aperture from atmospheric pressure into the first pumping stage.
Grids are also commonly utilized for sampling ions from atmospheric ion sources utilized in ion mobility spectrometry (IMS). Generally, for IMS analysis ions are pulsed through grids down a drift tube to a detector as shown in U.S. Pat. No. 6,239,428B1 to Kunz (2001). Great effort is made to create planar plug of ions in order to maximize resolution of components in the mobility spectrum. These devices generally are not continuous, nor do they require focusing at extremely high compression ratios. Our own U.S. patent application Ser. No. 09/877,167 (2001) and Ser. No. 10/449,147 (2003) describes high transmission elements, single layer and laminated, which allow the passage of substantially all of the ions or charged particles from a dispersive source through the element and be deposited as a small cross sectional area on a surface.
In general, prior art in the field of atmospheric optics, particularly that found for applications in mass spectrometry, has not addressed the spatial and temporal control and patterning requirements for applications in thin film deposition and printing.